1. Field of the Invention
The present invention relates to a wiper blade, which wipes a wiping surface, such as a windshield surface of a vehicle.
2. Description of Related Art
A tournament wiper blade is well known. The tournament wiper blade has a lever assembly, which includes a plurality of levers that are rotatably connected together. Since the levers are connected in a tournament fashion, the height of the wiper blade becomes relatively high. Therefore, upon receiving wind, which is applied to a running vehicle, the tournament wiper blade tends to increase resistance and wind noise or even blocks a driver's view in some cases.
To address the above disadvantages, Japanese Unexamined patent Publication No. 2001-504779 discloses a lever-less wiper blade. In the lever-less wiper blade, backing plates, each of which is shaped into a predetermined curved shape and serves as a spring member, are fitted to backing grooves of a wiper strip. A holder, to which a wiper arm is connected, is directly secured to the backing plates. In this way, the levers are eliminated in the lever-less wiper blade. In the lever-less wiper blade, urging force, which is received from the wiper arm to urge the wiper blade against a wiping surface, is applied directly to the backing plates. When the wiper blade wipes the wiping surface, the wiper strip is flexed to conform to the curvature of the wiping surface due to the spring characteristics of the backing plates.
In the above-described Japanese Unexamined patent Publication No. 2001-504779, the urging force of the wiper arm is spread along the length of the wiper strip through the backing plates. However, the urging force is applied to the backing plates through the holder secured to the longitudinal center of the wiper blade. Thus, excessive force is concentrated in the holder, so that the urging force is unequally distributed along the length of the wiper strip. The unequal distribution of the urging force causes generation of a water streak on the wiping surface (phenomenon known as “wiper streaking”) at the time of wiping, for example, rain droplets on the wiping surface.
Japanese Unexamined Patent Publication No. 49-92726 discloses a wiper blade, in which a wiper strip is supported through an elongated single lever that is connected to a wiper arm. In this wiper blade, a backing plate, which serves as a spring member and is curved to a predetermined shape, is fitted to the wiper strip to conform to the curvature or contour of the wiping surface.
The single lever is made of thermoplastic resin and is elongated along the entire length of the wiper strip. Also, the single lever receives the wiper strip in a rail-like continuous groove, which extends along the entire length of the single lever. Notches are provided along the length of the single lever to facilitate flexing of the single lever. However, since the single lever holds the wiper strip along the entire length of the wiper strip, the single lever prevents the wiper strip from properly conforming to the curvature of the wiping surface at the time of wiping the wiping surface. If the rigidity of the single lever is reduced to allow the wiper strip to properly conform to the curvature of the wiping surface, the single lever cannot properly spread the urging force of the wiper arm along the length of the wiper strip. Therefore, similar to Japanese Unexamined patent Publication No. 2001-504779, the wiper blade leaves a water streak on the wiping surface at the time of wiping the wiping surface, resulting in improper wiping performance.